1. Technical Field
The present invention relates to a polling method of a piezoelectric element and a method of manufacturing an inertial sensor using the same.
2. Description of the Related Art
Recently, as a small, light inertial sensor is easily manufactured by using an MEMS technology, its application range has been expanded to home appliances over an existing market. As the function of the sensor is continuously developed, the inertial sensor has been developed from a uniaxial sensor capable of detecting an inertial force of a single axis using a single sensor to a multi-axis capable of detecting an inertial force of a multi-axis of at least two axes using a single sensor.
Meanwhile, the piezoelectric element has been variously used for various actuators, sensors, or the like, by being deformed when voltage is applied to the piezoelectric element and generating charges a when force is applied to the piezoelectric element from the outside. In addition, the piezoelectric element uses various materials such as Aln, ZnO, quartz, or the like. However, PZT having a piezoelectric constant has been mainly used in various applications.
In order to improve the characteristics of the piezoelectric element, most of the piezoelectric elements are subjected to a polling process before being operated after the piezoelectric element is manufactured. The polling process is to improve the piezoelectric characteristics by applying heat and voltage.
Meanwhile, as a method of implementing a low-price micro angular velocity sensor, a capacitive method and a piezoelectric method have been mainly used. Further, the piezoelectric method can implement an atmospheric pressure packaging without needing to implement a vacuum packaging, as compared to the capacitive method.
In more detail, FIG. 1 is a schematic configuration diagram of an inertial sensor according to the prior art. As shown in FIG. 1, the inertial sensor 100 is configured to include a sensor unit 110, an ASIC chip 120, a molding unit 130, a wire 140, and a lead frame 150.
The sensor unit 110 is configured to include a driving body 111, a flexible substrate part 112 on which a driving electrode and a detection electrode are formed, a support body 113, an upper cap 114, and a lower cap 115.
By the above configuration, the driving body 111 is driven up and down, left and right/front and back or a complex direction thereof by applying voltage to the driving electrode. As a method for packaging an element in a micro size at low cost, a QFN or an LGA package has been mainly used. The package method is a method of performing an EMC molding process, mounting an element on a lead frame, and filling the entire surrounding of the element with epoxy. There is a need to protect the driving body 111 during the EMC molding. To this end, there is a need for a structure protecting the driving body 111 from an EMC epoxy or an external environment.
However, the piezoelectric element may deteriorate the polling characteristics while being subjected to a high-temperature packaging process by polling an individual chip and packaging it in the state of the substrate state before being packaged. In serious cases, the entire polling is released.
Therefore, it is most preferable to perform the polling after the element is packaged. In this case, as shown in FIG. 2, a terminal 112c is formed as many as the number of driving electrodes 112b and detection electrodes 112a to be polled. All the terminals should each be led and the electrode pads are required more than needs since the voltage and heat should be applied thereto. As a result, there are problems in that the size of the element is increased and the number of unused terminals is increased.